1. Field of the Invention
The present invention relates to a rechargable battery, and in particular to an apparatus and method of reducing charging time of a battery.
2. Background of the Related Art
FIG. 1 is a simplified block diagram showing a conventional charging machine for charging a battery with a plurality of battery units (hereafter xe2x80x9cmulti-batteryxe2x80x9d) with Li-Ion cells. The charging machine of FIG. 1 includes an AC adaptor 10 that converts an AC power to DC, a step-down charger 20 that transforms the converted DC voltage to a target DC voltage and outputs a charging current below a limited magnitude, and a battery selector 30. The battery selector 30 connects its power rail to one battery unit of a multi-battery 100 to supply a selected battery with the charging current.
The step-down charger 20 is designed such that its charging current is limited to remain within system capabilities. Thus, the limited current magnitude is determined so that a maximum electric power consumed by a system load 40 and used in charging the multi-battery 100 at the same time does not exceed an output rating of the AC adaptor 10.
The charging machine of FIG. 1 charges the battery units sequentially one at a time when charging a multi-battery 100. Namely, after a first battery unit is fully charged, the battery selector 30 disconnects its power rail from the first battery unit and connects its power rail to a next battery unit, and the next battery unit starts to be charged.
Assuming the multi-battery 100 is a dual-battery with two battery units A and B, as shown in FIG. 2 a charging operation of the battery unit B does not start until the battery unit A is completely charged. Therefore, a total charging time TTOT of the dual-battery is equal to sum of a charging time TA of the battery unit A and a charging time TB of the battery unit B. For example, it takes about 3 hours to charge a notebook computer with a single battery and about 6 hours to charge a notebook computer with a dual-battery.
A Li-ion battery has a feature that a charging current can increase without bound until the battery reaches a target voltage, e.g., 4.2V. However, the output current of the step-down charger 20 has been limited because of the output rating of the AC adaptor 10, so that a Li-ion battery is charged with the limited current until it reaches 4.2V. Since the limited current is constant, such a charging period is called a Constant Current (CC) mode. During the CC mode, a charged voltage increases gradually. After the charged voltage reaches the target voltage (i.e., time ta and tb in FIG. 2), it is maintained constant while a charging current tapers. Such a charging period is called a Constant Voltage (CV) mode because a charged voltage (i.e., VA and VB in FIG. 2) is held constant.
In other words, while a Li-ion battery is charged, the CC and CV modes are sequentially performed. In case of charging a dual-battery, charging current and voltage have respective curves as shown in FIG. 2.
As described above, however, the conventional charging machine has various disadvantages. From the graphs shown in FIG. 2, it can be noted that the charging power decreases gradually in the CV mode because the charging current tapers under the condition of constant voltage. Thus, a maximum charging power that can be supplied by a charging machine is not used in charging a multi-battery in the CV mode, and a total charging time of a multi-battery is therefore increased. Further, since a plurality of battery units of a multi-battery are charged one by one with a supportable electric power of an AC adaptor not being fully used, a total charging time of a multi-battery is in proportion to the number of its battery units.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
Another object of the present invention is to provide a multi-battery charging apparatus and method that reduces a charging time of the multi-battery.
Another object of the present invention is to provide a multi-battery charging apparatus and method that concurrently charges a plurality of the battery units of a multi-battery by dividing an assigned charging power among the plurality of the battery units to reduce an overall charging time.
Another object of the present invention is to provide a multi-battery charging apparatus and method that increases a percentage of assigned power used to assigned power when charging multiple batteries in a multi-battery power source.
Another object of the present invention to provide multi-battery charging apparatus and method that charges another battery unit with remaining charging power at the same time when an assigned charging power is not fully used to charge a first battery unit of a multi-battery to shorten an overall charging time of the multi-battery.
To achieve at least the above objects in a whole or in part and in accordance with purposes of the present invention, as embodied and broadly described herein, there is provided an apparatus for charging a multi-battery having a plurality of battery units that includes a charger that converts supplied electric power to a battery charging power having a current below a limited value, and a controller that receives the battery charging power from said charger, wherein the controller charges a first battery unit of the multi-battery, wherein the controller charges a second battery unit along with the first battery unit if a charging state of the first battery unit reaches a first preset condition, and wherein the controller charges the second battery unit with a current of the limited value when the first battery unit reaches a second preset condition.
To further achieve at least the above objects in a whole or in part, there is provided a method of charging a multi-battery having a plurality of battery units in accordance with the present invention that includes selecting a first battery unit of the multi-battery and charging the selected first battery unit, checking whether a charging state of the first battery unit reaches a preset value, selecting a second battery unit and charging the selected second battery unit along with the selected first battery unit when the preset value is reached, and charging the second battery unit with an assigned current of a limited value when the first battery unit reaches a sufficient charge.
To achieve at least the above objects in a whole or in part and in accordance with purposes of the present invention, as embodied and broadly described herein, there is provided an apparatus for charging a multi-battery having a plurality of battery units that includes a charger that outputs a battery charging power having an assigned level current, a battery selector that receives the assigned level current and is selectively coupled to the plurality of battery units, and a controller that controls the battery selector to charge a second battery unit in each of a first mode with a first level current below the assigned level current, a constant current mode and a constant voltage mode, wherein when the second battery unit is charged in the first mode a first battery unit is concurrently charged in the constant voltage mode to reduce an overall charge time of the multi-battery.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.